ArcGIS Pro 2.8 API Reference Guide
GeodesicArea Method (IGeometryEngine)
Example 

ArcGIS.Core.Geometry Namespace > IGeometryEngine Interface : GeodesicArea Method
The intput geometry.
Gets the geodesic area of a geometry.
Syntax
double GeodesicArea( 
   Geometry geometry
)
Function GeodesicArea( _
   ByVal geometry As Geometry _
) As Double

Parameters

geometry
The intput geometry.

Return Value

The calculated geodesic area in square meters. If the geometry is empty, then zero is returned.
Exceptions
ExceptionDescription
Geometry is null.
The method is not implemented for GeometryBag or Multipatch.
Spatial reference of geometryis an image coordinate system.
Example
var polygon = PolygonBuilder.CreatePolygon(new[]
{
  MapPointBuilder.CreateMapPoint(-10018754.1713946, 10018754.1713946),
  MapPointBuilder.CreateMapPoint(10018754.1713946, 10018754.1713946),
  MapPointBuilder.CreateMapPoint(10018754.1713946, -10018754.1713946),
  MapPointBuilder.CreateMapPoint(-10018754.1713946, -10018754.1713946)
}, SpatialReferences.WebMercator);
var area = GeometryEngine.Instance.GeodesicArea(polygon);

// area is close to 255032810857732.31
Requirements

Target Platforms: Windows 10, Windows 8.1

See Also

Reference

IGeometryEngine Interface
IGeometryEngine Members